Modeling and Simulation of Three-phase ac-dc Converter-Fed dc Drive Systems with Uniform Pulse-Width Modulation Control

Abstract

A three-phase ac-dc GTO (gate turn off) thyristor converter-fed dc motor is studied employing uniform pulse-width modulation (UPWM) scheme, and verified by computer simulation. It is found to offer good performance. It offers only two-quadrant operation because of the unidirectional current conduction nature of GTO's. A four-quadrant converter that employs a single six-GTO bridge converter and four thyristors serving as a reversing switch is described. The four-quadrant dc drive employing the proposed converter and the control structure including speed and current control loop is also presented. Simulation results with a separately excited dc motor are given for steady-state and transient responses of the drive.